Excavations 1293 Airport Road Beaver, WV Phone: (304) Fax: (304) Vincent J. Giblin, General President

This material was produced under grant number 46C5-HT16 from the Occupational Safety and Health Administration, U.S. Department of Labor. It does not necessarily reflect the views or policies of the U.S. Department of Labor, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.

Operating Engineers National Hazmat Program

Excavation u An excavation is a man-made cut, cavity, trench or depression in the earth surface that is formed by earth removal

Operating Engineers National Hazmat Program Soil Mechanics u Tension Cracks - Usually form at a horizontal distance of 0.5 to 0.75 times the depth of the trench. u Sliding - Sliding or sluffing may occur as a result of tension cracks u Toppling - Occurs when the trench’s vertical face shears along the tension crack line and topples into the excavation

Operating Engineers National Hazmat Program Soil Mechanics u Subsidence and Bulging - An unsupported excavation can create an unbalanced stress in the soil, which in turn, causes subsidence at the surface and bulging of the vertical face of the trench. If uncorrected this can cause face failure and entrapment of workers in the trench.

Operating Engineers National Hazmat Program Soil Mechanics u Heaving and Bulging - Caused by downward pressure created by the weight of adjoining soil. This pressure causes a bulge in the bottom of the cut u Boiling - Upward water flow into the bottom of the excavation

Operating Engineers National Hazmat Program

Unit Weight of Soils

Operating Engineers National Hazmat Program Determination of Soil Type u Stable Rock u Type A Soil u Type B Soil u Type C Soil u Layered Strata

Operating Engineers National Hazmat Program Stable Rock u Stable rock is a natural solid mineral matter that can be excavated with vertical sides and remain intact while exposed. u Usually identified by a rock name such as granite or sandstone.

Operating Engineers National Hazmat Program Type A Soil u Cohesive soils with an unconfined compressive strength of 1.5 tons per square foot (tsf) or greater u Clay, Silty Clay, Sandy Clay, Clay Loam u No Soil is Type A if it is fissured, is subject to vibration, has been previously disturbed, or has seeping water

Operating Engineers National Hazmat Program Type A Slope

Operating Engineers National Hazmat Program Type A Single Bench

Operating Engineers National Hazmat Program Type A Multiple Bench

Operating Engineers National Hazmat Program Type B Soil u Cohesive Soil with an unconfined compressive strength of 0.5 (tsf) or greater u Angular Gravel u Silt u Loam u Previously disturbed soils

Operating Engineers National Hazmat Program Type B Soil u Soils that meet the Type A Strength requirements but are fissured u Dry unstable rock u Layered Systems

Operating Engineers National Hazmat Program Type B Slope

Operating Engineers National Hazmat Program Type B Single Bench

Operating Engineers National Hazmat Program Type B Multiple Bench

Operating Engineers National Hazmat Program Type B Slope with a Shield

Operating Engineers National Hazmat Program Type C Soil u Cohesive with an unconfined compressive strength of 0.5 tsf u Granular Soils (Gravel, Sand, Submerged Soil) u Submerged Rock u Soil from which water is freely seeping

Operating Engineers National Hazmat Program Type C Slope

Operating Engineers National Hazmat Program Layered Strata (Soil) u When soil types are in layers, the soil must be classified on the basis of the weakest soil layer u Each layer must be classified individually if a more stable layer is below a less stable layer

Operating Engineers National Hazmat Program Type A over type B

Operating Engineers National Hazmat Program Type A over Type C

Operating Engineers National Hazmat Program Type B over Type A

Operating Engineers National Hazmat Program Type B over Type C

Operating Engineers National Hazmat Program Type C over Type A

Operating Engineers National Hazmat Program Type C over Type B

Operating Engineers National Hazmat Program Test Equipment and Methods for Testing Soil u Pocket Pentrometer u Shearvane (torvane) u Thumb Penetration Test u Dry Strength Test u Plasticity Test u Visual test

Operating Engineers National Hazmat Program Pocket Pentrometer u Pocket Pentrometer. Direct reading spring operated instrument used to determine the unconfined compressive strength of saturated cohesive soils. u Pentrometers have error rates of +/- 20% to 40%

Operating Engineers National Hazmat Program Shearvane (Torvane) u Used to determine the unconfined compressive strength of soil by pressing the blades of the vane into a level section of undisturbed soil, and the torsion knob is slowly turned until soil failure occurs.

Operating Engineers National Hazmat Program Thumb Penetration Test u Procedure involves an attempt to press the thumb firmly into the soil in question. u If the thumb makes an indentation with great difficulty, it is probably Type A u If the thumb penetrates no deeper than the thumbnail, it is probably Type B u If the thumb penetrates the full length of the thumb, probably Type C

Operating Engineers National Hazmat Program Dry Strength Test u Dry soil that crumbles freely or with moderate pressure into individual grains is granular. u Dry soil that falls into clumps that the break into smaller clumps (and the smaller clumps can be broken only with difficulty) is probably clay with a combination of gravel, sand or silt

Operating Engineers National Hazmat Program Dry Strength Test u If the soil breaks into clumps that do not break into smaller clumps, the soil is considered unfissured unless there is visual indication of fissuring

Operating Engineers National Hazmat Program Plasticity or Wet Thread Test u The test is done by molding a moist sample into a ball, then rolling it into a thin thread 1/8” in diameter by 2” long. The sample is held at one end, if the sample doesn’t break it is considered cohesive

Operating Engineers National Hazmat Program Visual Test u An evaluation of the whole excavation site by the competent person u Done Daily and after any change in conditions (rain, snow, underground obstruction, etc.) u Inspect the soil being removed from t he excavation. Verify that original soil type determination was correct

Operating Engineers National Hazmat Program Visual Test u Check for crack-line openings u Look for existing utilities that indicate the soil had been previously disturbed u Look at the open side of the excavation for layered soil types u Look for signs of bulging, boiling, or sluffing u Check spoil distance from the edge of the excavation

Operating Engineers National Hazmat Program Visual Test u Check spoil distance from the edge of the excavation u Inspect heavy equipment distance u Vibration u Traffic control u Barricades (Fall Protection) u Access / Egress from the excavation

Operating Engineers National Hazmat Program Trench Boxes

This material was produced under grant number 46C5-HT16 from the Occupational Safety and Health Administration, U.S. Department of Labor. It does not necessarily reflect the views or policies of the U.S. Department of Labor, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.

END This publication was made possible by grant numbers 5 U45 ES AND 5 U45 ES from the National Institute of Environmental Health Sciences (NIEHS), NIH. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIEHS, NIH.